Jahresbericht - Gesundheitsserver - Land Steiermark

Laboratory investigation:
Stool samples from 7 cases among the nursing home residents, 2 cases among the hospital patients and from
one case of the department staff were obtained and bacteriologically analysed. Faecal specimens obtained from
10 cases (2 cases of the nursing home residents, 7 cases of the hospital patients, 1 case of the hospital staff)
were sent to the laboratory responsible for norovirus diagnosis at the Austrian Agency for Health and Food
Safety, and analysed by reverse transcription- polymerase chain reaction (RT-PCR). The method is described
elsewhere (26, 27, 28). Sampling of food or environment was not performed.
Results
Outbreak Description
Between November 9 – 17, 2004, 18 of 23 permanent residents, and 7 of 18 members of the nursing and service
staff of a nursing home in a small village in a southern province of Austria, fell ill with diarrhoea, projectile
vomiting, or both. A second cluster of gastroenteritis occurred between November 11 and 28, 2004 at a hospital,
to which 8 of the 18 nursing home residents with acute gastroenteritis were referred. From November 11 - 28,
46 patients were hospitalised at this Department for Internal Medicine due to illnesses other than acute
gastroenteritis, and 60 staff members (clinicians, nurses and cleaners) were on duty at one of the two wards. Ten
hospital patients and 18 persons of the Department staff acquired nosocomial gastroenteritis.
The clinical features of gastroenteritis suggested norovirus as causative pathogen in both institutional clusters.
Vomiting was the prominent symptom, and diarrhoea was short-lived and less severe. The two institutional
clusters met the Kaplan criteria (24): stool samples - obtained from 7 cases among the nursing home residents,
from 2 cases among the hospital patients and from one case of the department staff - were negative for bacterial
pathogens; the median duration of illness was 2 days; vomiting occurred in 45 of 53 (85%) cases, and staff of
both institutions was involved. The incubation period was not ascertained.
Twenty-five persons (18 residents, 7 staff members) met the definition of a nursing home outbreak case, giving
an outbreak attack rate of 61% of a total of 41 persons exposed. Twenty-eight persons (10 hospital patients, 18
staff members) met the definition of a hospital outbreak case, giving an outbreak attack rate of 26.4 % of a total
of 106 persons exposed. On November 17, eight days after the index case had occurred in the nursing home,
stool samples from hospitalized cases among the nursing home residents (n = 2), from patients of the hospital (n
= 7) and from a staff member of the hospital were tested for norovirus. Norovirus was detected in 8 of the 10
stool samples. Both specimens from nursing home residents, 5 of 7 from patients, and the specimen from the
hospital staff member yielded norovirus gene group II (GG II). Figure 1 presents the epidemic curve of both
clusters and lists the results of RT-PCR testing.
Mode of transmission and spread from the nursing home to the hospital
The index case, a 91-year old woman fell ill on November 9. Of the service staff, none reported occurrence of
gastrointestinal symptoms within the 7 days prior to the date of onset of the index case. Of the visitors, a sister
of the index case reported to have suffered from symptoms compatible with norovirus infection until one day
before visiting the nursing home on November 7.
The occurrence of 16 cases within 2 days (November 10 – 11, 2004) following the occurrence of the index case
indicates an exposure to a common source of infection for these cases (figure 2). The information on the food
history of the nursing home cases does not suggest any association between food items and disease (data not
shown). All cases received their meals by means of finished food products, which were finally heated in the
nursing home kitchen before being served. The interview with the head of the nursing home staff yielded that
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